Japanese Patent Application Publication No. H10-335074 (hereinafter referred to as Patent Literature 1) discloses a lighting device including a light source. The lighting device detects brightness of a lighting area which should be lightened by the lighting device and calculates a difference between the detected brightness and a predetermined brightness. Then, the lighting device changes a light intensity ratio of the light source based on the calculated difference such that the lighting area comes to have the aforementioned predetermined brightness.